Launching device for projectiles

ABSTRACT

A launching device for a projectile comprises a barrel having an interior projectile chamber directly adjacent a muzzle opening at one end. The projectile is positioned behind the muzzle opening and is sealed from a propellant chamber directly behind the projectile chamber by means of a sealing member which permits expansion of the propellant chamber during the discharge of the projectile through the muzzle opening. The sealing member moves outwardly along the interior of the barrel, but is maintained in sealing engagement with the barrel to close off the propulsion chmaber even after firing of the missile. In one embodiment, the sealing member comprises a piston which moves along the interior of the barrel and is retained at the outer end thereof by retaining elements formed inwardly at the muzzle opening. In another arrangement, the sealing means comprises a membrane having its outer edges sealed around the periphery of the end of the barrel at the muzzle opening but extending backwardly to envelop the missile and to seal off the remaining portion of the interior of the barrel from the missile at the propulsion chamber. The propulsion chamber may be sealed at opposite sides by a piston arranged on each side of a propulsion charge or means for generating and introducing high pressure gases between the piston at each end. Instead of a piston, the device may comprise a membrane which is engageable with the barrel or even a flexible member in the form of a bellows which is secured to the interior of the barrel and expands outwardly in one or both directions.

United States Patent [1 1 GmbH, Munich, Germany Filed: Nov. 4, 1971 Appl. No.: 195,686

[30] Foreign Application Priority Data 1 Nov. 13, 1970 Gennany 2055805 [52] U.S. Cl. 89/l.70l, 89/1 B, 89/14 SB [51] Int. Cl F41f 3/02 [58] Field of Search 89/1.7 AW, 1.810, 1 B,

89/1 R, 14 SB,1F

[56] References Cited UNITED STATES PATENTS 1,416,828 5/1922 Holmes .89/14 SB 3,270,618 9/1966 Stott 89/43 3,476,048 11/1969 Barr et al. 89/14 SB 3,279,319 10/1966 Semonian et al 87/].810 2,499,379 3/1950 Garrett 89/1 B 3,404,598 10/1968 Angelos.... 89/1 B 3,490,330 1/1970 Walther 89/l.7

FOREIGN PATENTS OR APPLICATIONS 126,336 5/1919 Great Britain 89/l.70l

555,656 3/1957 Belgium 89/1.701

Primary Examiner-Samuel W. Engle Attorney, Agent, or Firm-McGlew and Tuttle Siiiifiiide [451 Apr. 2, 1974 1 LAUNCIIING DEVICE FOR PROJECTILES 75 Inventor: weairseiaabeie'wbreas'iiausei, 7 ABSTRACT German A launchin device for a pro'ectile comprises a barrel 3' g 1 [73] Assignee. Messerschmitt Bolkow mohm having an interior projectile chamber directly adjacent a muzzle opening at one end. The projectile is positioned behind the muzzle opening and is sealed from a propellant chamber directly behind the projectile chamber by means of a sealing member which permits expansion of the propellant chamber during the discharge of the projectile through the muzzle opening. The sealing member moves outwardly along the interior of the barrel, but is maintained in sealing engagement with the barrel to close off the propulsion chmaher even after firing of the missile. In one embodiment, the sealing member comprises a piston which moves along the interior of the barrel and is retained at the outer end thereof by retaining elements formed inwardly at the muzzle opening. In another arrangement, the sealing means comprises a membrane having its outer edges sealed around the periphery of the end of the barrel at the muzzle opening but extending backwardly to envelop the missile and to seal off the remaining portion of the interior of the barrel from the missile at the propulsion chamber. The propulsion chamber may be sealed at opposite sides by a piston arranged on each side of a propulsion charge or means for generating and introducing high pressure gases between the piston at each end. Instead of a piston, the device may comprise a membrane which is engageable with the barrel or even a flexible member in the form of a bellows which is secured to the interior of the barrel and expands outwardly in one or both directions.

2 Claims, 5 Drawing Figures PAIENIEDAPR 21974 3.800.656

sum 1 OF 2 Fig.1 s 1 a n Fig 2 21. 19 22 1 LAUNCHING DEVICE FOR PROJECTILES BACKGROUND OF THE INVENTION Field of the Invention This invention relates, in general, to missile launchers and, in particular, to a new and useful launching device for projectiles with a launching barrel having a projectile chamber adjacent an open muzzle behind which there is provided a variable area for the reception of a propellant means, especially a propellant charge.

SUMMARY OF THE PRIOR ART In the known launching devices for projectiles, the propellants for the projectiles whether produced by acceleration of pressure gases which have been produced from an exteriorly located pressure source and are fed into the launching barrel, or from ignition of a fuel charge housed in the launching barrel, produce after the discharge of the missile'from the barrel muzzle and after the discharge of eventually present contents of a flowable medium of high density from the rear barrel end which has been left open for this purpose, a great boom or loud emission. This explosion is due to the sudden expansion of the pressure gases into the open. Together with the further accompanying effects, such as muzzle fire and smoke developments, the explosion represents a great physical and psychological stress for the service personnel. The further consequences are permanent damage to health and even highly dangerous injuries to life. As a further drawback of this explosion, flash and smoke developments, there should be mentioned that an enemy observer has no difficulties whatsoever in ascertainingthe exact location of such a projectile barrel and to take effective counter measures against it.

For the previously mentioned reasons, there is mounted on a great number of known launching devices of the aforementioned type, a container, rigidly constructed, and varying in size with the individual amounts of pressure gases occuring, in front of the barrel muzzle and behind the open rear barrel end directed so as to cause, as far as possible, the launches to be recoilless. Each of these containers is divided into several expansion chambers by means of baffles and recoil valves, from which chambers small holes lead to the open. The energy of the pressure gases from the launching barrel is partially destroyed on the way through the expansion chambers and from the small holes to the open. The resulting dissipation of the launching explosion is however, many times, inadequate, especially in the case of recoilless launching constructions whose principle prevents the removal of substantial parts of the impulses of the pressure gases emanating from the launching barrel.

Aside from the sometimes only moderate noisedampening effect, the mounting of rigid containers of the abovedescribed type, on the launching barrel, brings along the following drawbacks:

First of all, the containers are relatively expensive as a. consequence of their complicated construction and production. In addition, they possess, because of the rigid construction of its outer walls, especially when they have been prepared for great pressure, a considerable construction volume and weight, which renders the transport and handling relatively difiicult. The aforementioned facts are especially disadvantageous on such launching devices that are portable and designated for only one use. In addition, the visible smoke and fire traces accompanying the pressure gas emission from the container holes still remains.

SUMMARY OF THE INVENTION The invention provides a launching device which, in contrast to the known noise-damper launching devices, is simple in construction and inexpensive in production and easy to handle and enables the launching of a projectile free of explosion, noise, smoke and fire traces on both recoil and recoilless projectile barrels, and even with highest power, for which the known noisedampening launching devices, by reason of their construction, could not be used.

This problem is solved by this invention in that the container for the propellant charge, after discharge of the projectile, remains gas-tight. In the arrangement of the invention, there is no necessity for the installation of rigid, bulky containers with complicated constructions for the noise'dampening, in front of the muzzle and, in recoilless constructions, behind the open rear end of the projectile barrel. Stresses from explosion, smoke and fire traces, attention to whose disadvantageous consequences has already been drawn in detail in another passage, are avoided through the special construction of the chamber for the reception of the propellant charge. The housing for the propellant charge remains gas-tight after discharge of the projectile from the projectile barrel. The construction can be realized with substantially less costs than the known noise-dampening arrangements and represents, in contrast to the latter, no impediment in the handling and transport of the launching apparatus.

From the plurality of the launching apparatuses, according to the invention, with launching barrels whose rear end is closed and which therefore have a recoil, the two arrangements described now are distinguished by a relatively simple and inexpensive construction.

In the one arrangement, the housing for the propellant charge which remains gas-tight after the discharge of the projectile is arranged behind the projectile chamber in the barrel, and one end is closed by a pressure-tight piston. This piston, which is movable over the complete length of the barrel is gas-tight in the launching barrel. With the acceleration of the projectile through the propellant charge, for example by pressure gas, which is fed into the provided housing from a source located externally of the launching barrel or by a propellant charge producing pressure gas which is placed into the provided housing, it moves, in the beginning, with the projectile in the direction of the barrel muzzle. In the area of the barrel muzzle, it is caught by the deflector which is larger in diameter than the projectile, and thereby makes an escape of the pressure gas into the open impossible.

In the other arrangement, the housing for the propellant charge remains pressure-tight after discharge of the projectile from the launching barrel by the sealing of a pressure-tight membrane, which is led around the barrel muzzle end and the rear end of the projectile in the projectile chamber adjacent the muzzle. This membrane moves along with the projectile, which has been accelerated by the propellant charge, out of the launching barrel, and it is turned inside out but does not open the propellant chamber but keeps the barrel and expanded propellant chamber sealed.

In a further embodiment of the invention, the launching device includes a barrel having a muzzle with a discharge opening for the projectile which is contained within the barrel and immediately behind the opening. A first piston member is arranged immediately behind the projectile and encloses one end of a propulsion chamber which is enclosed at the opposite end by a second piston. The propulsion chamber, for example, contains an explosive charge which, when it is ignited, tends to cause movement of the two piston elements in opposite outward direction. The one on one side of the explosive charge moves with the projectile to direct the projectile out through the muzzle opening and it is retained by an inwardly extending formational flange at the end of the barrel, so that when it arrives at'the muzzle end, it still maintains a seal of the interior of the barrel. The piston on the opposite side of the projectile closes off the inner end of a chamber which contains a flowable medium of high density. The opposite end of the barrel is provided with an opening which is closed by a member which is burstable or removable to permit the opening of this end and the outflow of the medium of high density after the propulsion charge is set off and the intermediate chamber bounded by the piston at each side. The second piston moves in a direction to cause the medium of high density to move in an opposite direction and rupture or remove the diaphragm to permit it to empty out of this end. The piston moves with the flowable medium until substantially all of itis discharged and it is retained at the rear end of the barrel by a flange formation or deflector so that this second piston also closes off the barrel, but at the rear end. In view of the complete recoilless operation, the construction is such that the two pressure-tight pistons, the projectile and the flowable medium of high density'are of a nature, volume, mass, etc., such that both pistons come to a standstill at the same moment at the respective outer ends of the barrel.

In a still further embodiment, the propellant chamber is sealed off by an expandible membrane on each side which expands outwardly in respective opposite direction to cause the missile ejection at one end and expulsion of the high density medium at the opposite end after the initiation of the propulsion means. The enclosing membrane for each side of the projectile space is formed as an expandible member which is folded inwardly into the barrel from each end. This membrane may be in the form of a bellow-like element.

Another embodiment is one in which the sealing membrane is secured to the outer end of the barrel at the muzzle end and at the opposite trailing end, and it is extended inwardly so as to surround the rear end of the projectile and the rear end of the flowable medium respectively, leaving space for the propulsion means between the inner ends of the opposite membranes. When the propulsion means is initiated in the space between the membranes, each moves outwardly in an opposite direction, the one to follow the missile which will be directed ahead of it out of the muzzle end and the other to follow the high density medium out of the recoil end. The construction may be such that the device is completely recoilless. For this purpose, the pressuretight membranes, the projectile and the flowable, high density medium are coordinated in respect to volume and size such that the membranes invert and expand outwardly to the fully inverted position at substantially the same time.

Accordingly, it is an object of the invention to provide an improved device for launching projectiles, and the like, which includes a barrel having an interior for accomodating the projectile which is separated from an interior portion containing the propulsion means, this separating means forming a seal which permits expansion of the propellant to launch the projectile, but maintains the expanded projectile chamber sealed after the discharge of the projectile.

A further object of the invention is to provide a missile launcher, which includes a barrel having a muzzle opening with a deflector at the opening, with means for mounting the projectile immediately behind the opening and a sealing piston immediately behind the projec- 'tile'which closes off a propellant chamber, the piston being movable outwardly-upon initiation of the propellant and launching of the missile to an outermost position directly adjacent the muzzle, at which it is engaged and held by the barrel and in which it seals the propellant chamber.

A further object of the invention is to provide a missile launching device which includes a propellant chamber defined in a barrel behind the missile to be fired through the muzzle of the barrel and which is sealed on respective opposite sides by movable members, such as pistons which move outwardly in opposite directions and including a flowable medium of high density arranged between the propellant charge chamber and the rear of the missile with means for permitting it to flow outwardly from the barrel after the missile is launched.

A further object of the invention is to'provide a missile launcher which is simple in designq rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the Drawings:

FIG. I is a longitudinal sectional view of a missile launching device constructed in accordance with the invention;

FIG. 2 is a view similar to FIG. 1 of another embodiment of the invention; and

FIGS. 3 5 are views similar to FIG. I of still further embodiments of the invention in which the launcher is recoilless.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENTS 'lant explosive charge 7.

ing. The barrel is provided with a closed rear end or wall 4. A radially inwardly extending wall defines a deflector or arrestor 5 for engaging a pressure-tight piston 8 which is mounted in the barrel for sliding movement and is located between the projectile 6 and a chamber for a propellant charge 7.

The projectile 6 may be, for example, an undercalibrated tank projectile which is centered in the barrel by means of a bearing ring 9. Piston 8, which is immediately behind the projectile 6, extends over the complete cross section of the barrel and is maintained in gas-tight association with the interior walls of the barrel.

The projectile chamber or propellant means chamber 10 includes a propellant means in the form of a propel- In accordance with the invention, the area which defines the propellant charge area, remains gas-tight even after discharge of the projectile 6 from the barrel muzzle 3. The propellant charge, in this instance, an explosive charge 7, is ignited by an ignition capsule 11 which, after ignition, causes the rapid movement of the piston 8 toward the muzzle opening 3 along with the projectile 6. Thereafter, the piston displaces the bearing ring 9 and is then captured or held by the arrestor 5 in the form of a retainer flange. When the piston arrives in this position, it closes off the outer end of the barrel and maintains the pressure gases in the expanded propulsion means chamber 10 from escaping to the open and this results in a positive explosion-free discharge of the projectile 6 without any visible smoke or fire traces.

The recoil launching arrangement 15, according to FIG. 2, is also designed to be portable and for one-time use only. It comprises a launching barrel 16, whose barrel muzzle is designated with 17 and whose closed rear barrel end is designated with 18. Into the launching barrel 16 projects a pressure-tight membrane or seal member 19, which is fastened pressure-tight with its outer edge to barrel muzzle 17. The membrane 10 extends from the barrel muzzle 17 over the inner wall of the projectile barrel 16 to the rear end of the projectile 20 and there over the entire local barrel cross section. This results in an all-around gas-tight combustion chamber orpropellant chamber 21, which in this embodiment, comprises a propellant charge 22. This combustion chamber 21 remains gas-tight even after discharge of the interior area 24 of the membrane 19 along with a projectile guide ring 23, and a projectile 20 out of the barrel muzzle 17. By the ignition of the propellant charge 22 through an ignition capsule 25, membrane 19 inverts itself or turns inside out and extends out of the launching barrel 16, as shown in dashdot lines in FIG. 2, but without disengaging from the barrel 16.

The launching device 31, according to FIG. 3, belongs to the recoilless construction types. lts launching barrel 32 includes muzzle opening 33 as well as a rear barrel end opening 34. An interior high density flow medium 41 is held in the rear of the barrel interior by a removable element or burst membrane 35. Retainers 36 and 37 are arranged in the muzzle adjacent the front and rear ends, respectively, of launching barrel 32. In launching barrel 32, there are arranged, axially one after the other, a projectile 38, for example, a tank projectile or a granate, a propellant charge 40 provided with an ignition capsule 39 and a filling 41 of flowable medium of high density. An example of a media suitable for such purpose is one which does not vaporize with increasing temperature and would be easily divisible, like water-oil solutions, gel-like substances which become fluid under pressure, and granular solid substances, for example, sand. Propellant charge 40 is separated from projectile 38, which is guided and lead by a guide ring 42 in launching barrel 32, as well as from the media 41 by gas-tight slide members or pistons 43, 44. Both pressure-tight pistons 43 and 44 form together with the launching barrel 32 a propellant charge chamber or propulsion chamber 45, which, as will be shown, also remains gas-tight even after the projectile is discharged and the media is discharged.

As a consequence of the reciprocal arrangement of the projectile 38, the propellant charge 40, the medium 41, and the pistons 43 and 44, the piston 43 fastened to projectile 38 moves in the direction of barrel muzzle 33 after ignition of the propellant charge 40 due to the influence of the resulting pressure gases. Simultaneously, piston 44 with the media 41, moves in the direction of the rear end 34, to cause a bursting membrane 35 to be destroyed and the medium to leave the launching barrel 32 through thenow opened rear barrel end 34. In the present case, the medium 41 consists of a flowable medium for the positive avoidance of a recoil and is so coordinated in volume to the projectile and piston masses, that both pistons 43 and 44 come to a standstill at the same time as they are engaged by retainers 36 and 37 of the projectile barrel 32. Piston 43, together with the other piston 44, seal against escape of the pressure gases from the combustion chamber 45 into the open.

Recoilless launching device 51, according to FIG. 4, differentiates from the aforedescribed ambodiment by the absence of pistons in launching barrel 52 and the absence of piston deflectors in the area of the barrel muzzle 53. In addition, it includes a rear, openly constructed barrel end 54, which is temporarily closed by a bursting membrane 55. Propellant charge 57, which is provided with an ignition capsule 56, is contained in a combustion or propellant chamber 61 defined within a container or bellows 58 which is pressure-tight and located in fixed position in the middle area of the launching barrel. This container 58 which is located between projectile 59 and a high density media 60 remains gas-tight and forms a gas-tight combustion chamber 61 even after discharge of the projectile and emission of the media.

In the recoilless launching arrangement illustrated in FIG. 5, there is arranged in a launching barrel 66, whose muzzle is designated with 67 and whose openly constructed rear end is designated with 68, a projectile 69 and a flowable medium 72, axially one after the other and without leaving of an interim space. Furthermore, two pressure-tight membranes or bags 73 and 74 project into launching barrel 66 one of which (73) is fastened pressure-tight with its edge in the area of the barrel muzzle 67 and the other (74) is fastened pressure-tight with its edge in the area of the rear barrel end 68 outside onto the launching barrel 66. The firstmentioned pressure-tight membrane 73 extends from the barrel muzzle 67 over the inner barrel wall area to the rear projectile end and thereover the entire local barrel cross section. A bearing ring for the projectile 69 is located on the inner wall area of this membrane 73, the other membrane 74 envelopes the medium 72. Both pressure-tight membranes 73, 74 form, together with the launching barrel 66, a gas-tight propulsion chamber or propellant charge chamber 76 which remains gas-tight even after the projectile and media are discharged. The propulsion means is supplied through a line 77 with a recoil valve 78 and comprises a pressure gas 70, serving as a propellant charge, which is fed from a pressure source 79.

In each of the embodiments of FIGS. 1-5 the launching device includes sealing means between the projectile chamber and the propellant chamber. In the embodiments of FIGS. 1 and 3 the sealing means comprises the pistons 8 and 43 respectively. In the embodiments of FIGS. 2 and 5 the sealing means comprises the membrane seal 19 and the similar membrane seal 73. In the embodiment of FIG. 4 the sealing means comprises the bellows 58.

In respect to FIG. 3, a first seal'comprises a piston 43 which seals off the space in the barrel 31 behind the missile mounting means 42. A second seal comprises the piston 44 which seals the space behind the propellant charge 40 toward the end 34 opposite to the muzzle end 33. Similar first seals comprise the piston 8 in FIG. 1, the member 19 in FIG. 2, the bellows 58 in FIG. 4 and the member 73 in FIG. 5. Similarly, the second seal comprises the closed rear wall 4 in FIG. I, the closed rear end 18 in FIG. 2, the piston 44 in FIG. 3, the bellows member forming the propellant chamber 61 on the closed end side of the explosive charge 57 of FIG. 4 and the bag-like member 74 in FIG. 5.

While'specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A launching device for a projectile comprising a smooth uninterrupted launching barrel having an opened end defining a muzzle through which a projectile is launched and an opposite axially aligned opened end for the discharge of a recoil medium, projectile mounting means for mounting a projectile in said barrel in a position pointed toward said muzzle, a first moveable seal piston in said barrel having at least a portion extending behind said mounting means and sealing the space in said barrel behind said projectile mounting means, an explosive propellant charge in said barrel on the opposite side of said first seal piston from said-projectile mounting means, and a second moveable seal piston in said barrel located between said propellant charge and said opposite end of said barrel, said first 8 seal piston being movable upon ignition of said explosive propellant charge in a direction toward said muzzle along with the projectile, said second seal piston being movable pon ignition of said explosive propellant charge in a direction toward the opposite opened end, holding means adjacent said muzzle end and the opposite end for holding said first seal piston and said second seal piston in sealing engagement with said barrel at said muzzle end and the opposite end respectively to block off the escape of gases from the explosive charge but permitting a predetermined movement of said first and second seal pistons in respective opposite directions away from said explosive charge after ignition of said explosive charge, and a dense fiowable medium in said barrel between said second seal and the opposite end with means for retaining the medium behind said second seal until ignition of said explosive charge for permitting the outflow of the dense fiowable medium and the movement of said second seal toward the opposite end after ignition of said explosive charge.

2. A launching device for a projectile comprising a cylindrical smooth-bored substantially uniform diameter continuous launching barrel having an opened end defining a muzzle through which a projectile is launched and an axially aligned opposite end, a projectile adapted to be positioned in said barrel adjacent the muzzle end and at position pointed toward said muzzle, a first seal having at least a portion extending behind said projectile and sealing the space in said barrel behind'said projectile, means for supporting a projectile between said first seal and said muzzle, an explosive charge in said barrel on the opposite side of said first sea] from said muzzle, a second seal located between said propellant charge and said opposite end of said barrel, said first and second seals comprising movable piston members movable toward said muzzle and said opposite end respectively, and a dense fiowable medium in said barrel between said second seal and the opposite end with means for retaining the medium behind said second seal' until ignition'of said explosive charge for permitting the outflow of the dense flowable medium and the movement of said second seal toward the opposite end after ignition of said explosive charge, said barrel having an inwardly extending portion adjacent each end engageable with respective first and second seals after they move to the respective ends to close said barrel to seal off the escape of gases from the ignition of said explosive charge. 

1. A launching device for a projectile comprising a smooth uninterrupted launching barrel having an opened end defining a muzzle through which a projectile is launched and an opposite axially aligned opened end for the discharge of a recoil medium, projectile mounting means for mounting a projectile in said barrel in a position pointed toward said muzzle, a first moveable seal piston in said barrel having at least a portion extending behind said mounting means and sealing the space in said barrel behind said projectile mounting means, an explosive propellant charge in said barrel on the opposite side of said first seal piston from said projectile mounting means, and a second moveable seal piston in said barrel located between said propellant charge and said opposite end of said barrel, said first seal piston being movable upon ignition of said explosive propellant charge in a direction toward said muzzle along with the projectile, said second seal piston being movable pon ignition of said explosive propellant charge in a direction toward the opposite opened end, holding means adjacent said muzzle end and the opposite end for holding said first seal piston and said second seal piston in sealing engagement with said barrel at said muzzle end and the opposite end respectively to block off the escape of gases from the explosive charge but permitting a predetermined movement of said first and second seal pistons in respective opposite directions away from said explosive charge after ignition of said explosive charge, and a dense flowable medium in said barrel between said second seal and the opposite end with means for retaining the medium behind said second seal until ignition of said explosive charge for permitting the outflow of the dense flowable medium and the movement of said second seal toward the opposite end after ignition of said explosive charge.
 2. A launching device for a projectile comprising a cylindrical smooth-bored substantially uniform diameter continuous launching barrel having an opened end defining a muzzle through which a projectile is launched and an axially aligned opposite end, a projectile adapted to be positioned in said barrel adjacent the muzzle end and at position pointed toward said muzzle, a first seal having at least a portion extending behind said projectile and sealing the space in said barrel behind said projectile, means for supporting a projectile between said first seal and said muzzle, an explosive charge in said barrel on the opposite side of said first seal from said muzzle, a second seal located between said propellant charge and said opposite end of said barrel, said first and second seals comprising movable piston members movable toward said muzzle and said opposite end respectively, and a dense flowable medium in said barrel between said second seal and the opposite end with means for retaining the medium behind said second seal until ignition of said explosive charge for permitting the outflow of the dense flowable medium and the movement of said second seal toward the opposite end after ignition of said explosive charge, said barrel having an inwardly extending portion adjacent each end engageable with respective first and second seals after they move to the respective ends to close said barrel to seal off the escape of gases from the ignition of said explosive charge. 